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Old 25th January 2018, 05:07 AM   #61
Jeff Mills is offline Jeff Mills
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Join Date: Nov 2017
Are DP3 & DP4 zener diodes? They would test as a double diode and not a resistor - correct?

Also pins 9 & 10 on the TL494 (drivers) read 4.48V is this enough to drive the gates of IRF3205 through 47 ohm gate resistors? (See my previous post). I thought I read that the TL494 has a internal 5 volt voltage regulator so it also defective?

Thanks guys.
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Old 25th January 2018, 03:08 PM   #62
Jeff Mills is offline Jeff Mills
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I think the TL495 data sheet answered my question.

"Internal Regulator provides a stable 5-V reference supply, with 5% tolerance"

5% of 5V is .25V so if I'm understanding the data sheet correctly, pins 9&10 (E1&E2 / drivers) should be between 4.75V to 5.25V. I measure 4.48V on pins 9&10 which is outside of the 5% tolerance. So the TL495 on this board seems to be defective. Am I correct in my thinking here?

TL495 datasheet link ---> https://www.google.com/url?sa=t&sour...MbZIDaGYKDiWJf

Last edited by Jeff Mills; 25th January 2018 at 03:16 PM.
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Old 25th January 2018, 03:35 PM   #63
Jeff Mills is offline Jeff Mills
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Also you'll see here that DP3 (zener diode) is testing as a 132.9 ohm resistor. But DP4 tests as a double diode.

I believe since the DP3 zener diode is also defective and could be the reason why the bank of IRF3205s go up in flames when I apply ~ 12V to the board.

Is this also correct thinking?
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Old 14th February 2018, 08:02 PM   #64
Formas is online now Formas  Jamaica
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By using that particular device tester, its best you do an out of circuit test on the devices you suspect. my experience thats for a standalone devices under test and not incircuit.
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Old 16th February 2018, 05:24 PM   #65
Perry Babin is offline Perry Babin  United States
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You are reading the parallel diode/base-emitter. The one that doesn't read as a double, has an open driver transistor.
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